1. Field of the Invention
The present invention relates to an ink composition, an ink cartridge including the ink composition and an inkjet recording apparatus including the ink cartridge. More particularly, the invention is directed to an ink composition that exhibits a decreased bleeding between colors of a printed image, and water fastness of a printed image and dry and wet rub fastness are improved, an ink cartridge including the same and an inkjet recording apparatus including the ink cartridge.
2. Description of the Related Art
In general, coloring agents embody their inherent colors by selectively absorbing or reflecting visible light, and are classified as dyestuffs and pigments.
Dyestuffs are used in any material to be dyed, such as fibers, leathers, furs, papers thereby providing considerable fastness to daylight, washing, friction, etc. Pigments are coloring matters in the form of particulates, and are not directly dyed to the surface of the material adhered thereto, by physical means (such as, adhesion, and the like) thereby providing their inherent colors.
Dyestuffs are dissolved in solvents such as water, organic solvents and mixtures thereof. Pigments are generally insoluble in the solvents, and thus it is most important to disperse the pigment particulates homogeneously in a solvent, carrier or vehicle, thereby stably maintaining the dispersed state without re-aggregation.
Dyestuff-type ink is very superior in long-term storage stability, maintaining its homogeneity, and its clear color and brightness. However, dyestuff-type inks are weak in water fastness and light resistance.
Pigment-type ink has high optical density (OD), and superior water fastness and light resistance, and exhibits little bleeding between colors. Pigment-type inks exhibit poor color clearness and weak long-term storage stability compared to dyestuff-type ink. Also, images printed using pigment-type inks have weak dry and wet rub fastnesses.
When printing in colors (multicolor printing) with dyestuffs or pigments, bleeding at interfaces of each color occurs, and thus the clearness of the images is weakened.
To improve rub fastness and color fastness by decreasing mobility of a coloring agent on receptors such as paper, an ink composition for ink-jet printing comprising a pigment, a water-soluble resin and a specific alcohol are used as disclosed in U.S. Pat. Nos. 5,172,133 and 5,529,616.
However, the ink composition for inkjet printing is ejected through nozzles, and thus should have a low viscosity. The amount of polymer binder used in the ink composition is limited. Thus, the amount of polymer binder used cannot bind sufficiently pigment particles to the top of a receptor, thereby providing unsatisfactory rub fastness and color fastness.
As another approach to improve rub fastness and color fastness by decreasing mobility of a coloring agent on receptors, a method using chelating of metal ions (U.S. Pat. No. 4,694,302), a method using a reaction of a cation and an anion (U.S. Pat. No. 5,623,294), and a method using a reaction of polymer (U.S. Pat. No. 5,629,359) have been disclosed. However, the method using chelating of metal ions has difficulty in obtaining long-term storage stability due to a reaction of each ink constituent and metal ions contained in an ink, and the method using a reaction of a cation and an anion also has poor performance due to a reaction of a substrate and the ions as well as a reaction of ink constituents. Also, the method using a reaction of a polymer has an environmental burden due to unreacted monomers, and a further need for a curing apparatus and curing time, in addition to the difficulty in obtaining long-term storage stability.